1. Field of the Invention
The present invention relates to improvements in an apparatus and method for editing and creating video images, and more particularly, to an apparatus and method for editing and creating video images which is capable of effecting a high quality and high speed real-time adjustment of a nib diameter in accordance with an applied pressure of a stylus pen and effecting soft edge processing corresponding to the nib diameter.
2. Description of the Prior Art
A general conventional apparatus for editing and creating video images includes, among other things, an input device composed of a stylus pen, tablet, keyboard and other such input components, an operation processor for processing various data signals from the input device, and a display device. An image drawn on the table by an operator using the stylus pen is displayed in real time on the display device.
In such an apparatus for editing and creating video images, however, the operator must usually select a pen of proper diameter from among specified stylus pens, and draw on the tablet using the selected pen. In actuality, only a few stylus pens are available, and it is difficult to contact the pen on the tablet in a sufficiently delicate manner to obtain precise corrected works having accurate and smooth features.
In the outer periphery of a painted image drawn using an actual paint brush, a spontaneous soft boundary (hereinafter called a soft edge) is usually formed by a delicate mixing of the brush color and the paper color. In the apparatus for editing and creating video images using a stylus pen, it is indispensable to subject the video signal to so-called soft edge processing in order to realize a soft edge in the video image.
A soft edge processing method has been developed for this kind of apparatus for editing and creating video images, in which the touch of the soft edge processing itself is varied by the stylus pen pressure and fed back (e.g., Japanese Laid-open Patent No. 62-35980).
Such a soft edge processing method can simulate existing painting tools (brushes, pens, etc.) to a certain extent, and realize various pen touches of painting tools in a nearly satisfactory manner.
Generally, when painting a drawing or correcting a drawing, however, in order to more precisely realize delicate pen touches of painting tools such as brushes, it is more important to vary the diameter of the nib depending on the pressure applied by the stylus pen, rather than to vary the degree of soft edge processing itself by the stylus pen pressure and to feed it back.
In the actual world of painting, even when the same brush and same color are used, the touch (pressure) of the brush varies significantly depending on the medium that is painted (for example, the pressure applied when painting on paper and that when painting on cloth differs by about two to one). Therefore, in order to simulate the brush perfectly, it is necessary to effect processing in harmony with a change of nib diameter depending on the nib pressure and the material to be painted on, aside from the change of the degree of soft edge processing. In the conventional soft edge processing method of varying only the degree of the soft edge processing according the stylus pressure and feeding it back, the painting tools cannot be simulated completely, and delicate touches of the painting tools cannot be reliably reproduced.
Further, in the conventional soft edge processing method, it is extremely difficult to process the soft edge following a fast moving speed of the stylus pen, and hence it is necessary to restrict the pen moving speed within a certain speed or to use an expensive electronic device.